Ministers and bosses are wrong to try to make people return to the office against their will, Keir Starmer has said.
The Labour leader claimed attempts to force workers back were "wrongheaded" and were contrary to the progress made on flexible working during the pandemic.
Some Cabinet ministers are planning a "big push" to get their staff back to Whitehall from next month - and want employers to do the same.
Chancellor Rishi Sunak has highlighted the benefits of office working, saying it had been "really beneficial" working in an office environment early in his career.
But No 10 has said they would follow a "cautious" approach to civil servants returning to their offices, with departments able to be flexible in how the process is managed.
In an interview with the Guardian, Mr Starmer said it was wrong for people to be made to go back in when the Government had asked them to work from home in the first place.
This was especially the case if they were being threatened with pay cuts or the loss of London weighting from their salaries.
“I just think it’s wrongheaded,” he said. “People were asked to work at home. And they did, and they worked very hard.
"The idea now that people are being threatened, if they don’t come in when there’s no good reason – it’s wrong.”
Mr Starmer said that the pandemic had "absolutely destroyed the myth" that people working from home were not actually working.
He added that it was “a bit rich” of Boris Johnson to encourage people to get back to the office when he regularly works from his grace-and-favour country home at Chequers.
The move to more flexible working is widely regarded to have been one of the few good things to have come out of the last 18 months.
Both unions and employers' groups have highlighted the benefits of flexible working to both companies and their staff.
Labour has promised a right to flexible working - employees can currently request it but businesses are only obliged to consider it in a "reasonable" manner.
Recent research from the TUC found that 82% of workers want to work flexibly in the future, rising to 87% among female employees.
Yet 71% of flexible working requests were rejected in 2020, up from 53% the previous year.
